A novel modem model insensitive to the effect of the modulated carrier and the demodulated-signal phase adapted for capacitive sensors
A novel modem model insensitive to the effect of the modulated carrier and the demodulated-signal phase adapted for capacitive sensors
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DOI：
10.1016/j.measurement.2023.112734
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发表时间：
2023-03-21
期刊：
影响因子：
5.6
通讯作者：
Zhou, Zebing
中科院分区：
文献类型：
--
作者：
Li, Ke;Chen, Decong;Zhou, Zebing
差动桥式电容传感器在精密仪器测量领域有着广泛的应用，其中调制解调器是实现微小差动电容检测的关键技术。由于调制解调器采用基于正弦调制载波和开关模拟解调的通用结构，载波的稳定性和解调信号之间微小的相位差及其波动性将不可避免地限制调制解调器的性能，并进一步恶化电容灵敏度。本文提出了一种基于调制阶跃正弦载波的新型调制解调器，理论分析表明，这种新型结构可以显著降低上述因素的影响。最后，一个联合评估电路的建立，初步测量调制解调器的噪声，实验结果表明，相对电压噪声功率谱密度为7 ppm/Hz 1/2，在1 mHz的新型调制解调器，2倍以上的正弦载波。
The differential bridge-type capacitive sensors are widely applied in many precise instrumental measurement fields, where the modem is a key technology to realize the detection for a tiny differential capacitance. A universal structure based on a modulated sine carrier and a switched analog demodulation is adopted, so two factors including the carrier's stability and the slight phase difference with its fluctuation between demodulated signals will inevitably limit the modem performance, and further deteriorate the capacitance sensitivity. In this paper, a novel modem based on a modulated step sine carrier is proposed, and the theoretical analysis indicates that the novel structure can significantly reduce the effects of aforesaid factors. Finally, a joint evaluation circuit is built to preliminarily measure the modem noise, and experimental results demonstrate a relative voltage noise power spectral density of 7 ppm/Hz1/2 at 1 mHz for the novel modem, two times better than that with a sine carrier.